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RE: OD Speedo numbers

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Subject: RE: OD Speedo numbers
From: (Bert Palte)
Date: Sat, 25 Apr 98 11:15:04 +0200
>I know there are no stupid questions but what is a CB or RB car?  I have
>never heard of those identifiers before
When Julius Caesar wrote his reports on the progress of the war in Gallia,
he started by stating in the very first line  that this territory is divided
into three parts.
Similarly, the MGB population is divided into two groups: the chrome bumper
versions and the rubber bumper versions. 
(The change occurred somewhere midway 1974).
As Rick and Mike have pointed out correctly, this was what I had in mind
when I said CB and RB.
I held these abbreviations to be self-evident, but then I was mistaken. 

Sorry guys, I'll try to be more explicit next time!

BTW my speedo says "SN 5144/24A 800" but then 800 is the number of
revolutions per kilometer, not per mile.
This is on a 1970 CB (=chrome-bumper) car, European version, LHD with
old-style fascia panel, no overdrive.

My non-o/d (o/d means overdrive) gearbox on this car has 10/26 teeth/teeth
ratio (=0.3846).
An o/d gearbox for the same car has 8/21 teeth/teeth ratio (= 0.3809).
(gives a 1 percent difference = negligible).

A later type o/d gearbox (for the RB=rubber bumper car) has a 6/21
teeth/teeth ratio (=0.2857).
This would give a difference of 26 percent in speedo indication if put into
a CB car.

Note: if you want to change the speedo gear ratio in the gearbox, you have
to replace BOTH gears, not just one!
This subject has been discussed on this list earlier, in January 1996.

Have a nice weekend!


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